This invention relates generally to an optoelectronic semiconductor device, and more particularly to an optoelectronic semiconductor having therein memory elements which are responsive to injected light for erasing memory and/or for modulating injected light.
Along with the development of the optical information processing technique, there has arisen an ever increasing demand for miniaturization of the space-consuming optical system.
In solving this technical problem, it is required that an optical device be integrally combined with a semiconductor device produced by semiconductor integrated circuit technology.
Also, for providing an optoelectronic semiconductor device having new capabilities, it is required that the optical devices be combined with semiconductor devices as an organic whole. The optical modulator which has been hitherto used, however, is of single crystal using electro-optic effect to cause modulation, and it is difficult for this material to mate with the conventional semiconductor device. As for the optical waveguide which has been hetherto used in propagation of light, a thin film whose refractive index is higher than that of a glass substrate is deposited on the substrate to function as an optical waveguide.
Otherwise, an organic solid insulating material which is essentially transparent to the light is fitted to same substrate to construct the optical waveguide, or the high index-of refraction region of a layered compound semiconductor device such as a GaAs or Ga.sub.x Al.sub.1-x As is used as the waveguide.
Some of such materials, however, are difficult to treat electrically, and others are not amenable to batch production.
It is most desirable to combine an optical device with an integrated circuit on an Si substrate according to the integrated circuit manufacturing processes. It is desired to build an optical device directed to a particular purpose into an electric integrated circuit on one and the same substrate. Therefore, the first object of this invention is to provide an optical modulator which can be easily made by combining an optical waveguide and a semiconductor device on an Si substrate so as to constitute an organic whole according to the integrated circuit technology.
The second object of this invention is to provide an optoelectronic semiconductor device which is an integral combination of waveguide and semiconductor memory on one and the same substrate, and is capable of controlling the threshold gate voltage value of the semiconductor MIS memory in response to the guided light.
The third object of this invention is to provide an optoelectronic semiconductor device using its semiconductor film per se as an optical waveguide which device is capable of modulating the light through the interaction between the guided light and the stored electronic charges or local semiconductor surface charges due to the stored memory charge.